The time is near.

[LGT Kirby]

I first would like to thank SL-i and all it's members for all the help over the past year with my car. In addition to that, I'd like to appologize for my lack of updates on my car in the member's ride.

Basically, the time has come to upgrade the engine. I'm nearly complete with the suspension, and the last year of reading about swaps is finally going to be tested.

The only issue is, which one do I chose?

I have narrowed it down to 2 different choices. Keep in mind that I am wanting to run a turbo setup.

Obviously the full out "do it right the first time" way. Complete WRX or STi swap, including merging the harness and all that wonderful stuff.

The 2nd choice being what I'd really rather do, but I'm not 100% sure about the details needed. This would be running a turbo shortblock (WRX or STi block) with the stock 2.5 DOHC heads.

I don't have any questions about the first choice. Its pretty straight forward. Spend countless hours of my life merging the harness, or pay $1000 I spent countless hours of my life making to pay somebody to do the work for me.

My real question is about the 2nd choice. I have read about having to plumb the 2.5 DOHC heads previously, when I used to own a Legacy SS. The 2.5 heads are a great upgrade, but have to be plumbed for the oil and coolant to go to the turbo. Correct?

What this all comes down to is the following.

-If I can put my stock 2.5 DOHC heads (plumbed correctly) on a 2.0 WRX or 2.5 STi shortblock, I really don't have to mess with any wiring. That is my MAIN question. Besides the few sensors on the block itself, there is no real "wires" going to the ECU to be able to tell it that the block is different. So TECHNICALLY I should be able to make sure the sensors are the correct match to the ECU, put on my STOCK heads with the custom work done to them, and call it good?

I have seen a setup using a WRX intake manifold on a STi block with the stock 2.5 N/A DOHC heads. The intake manifold has the height for the turbo inlet to go under, and if you switch over all the stuff from the 2.5 N/A intake to the WRX intake, the ECU again wouldn't be able to notice any differance. But there another issue there. My DOHC heads are Phase 1, and I'm pretty sure the USDM WRX (02+) is all Phase 2. Right? The issue here being the ability to mount the intake to the heads. Phase 1 has all 4 bolts in a striaght line, mounting the intake to the heads. Phase 2 has 2 different offsets, making it impossible to mount them without doing some custom stuff. So I'm not sure what he did to make that work.

To get around that I'd assume using an older (Phase 1) turbo intake manifold instead. Like a Legacy SS or any JDM intake manifold. This runs into a WHOLE different situation, including the water crossover pipe. The pipe is different for pretty much all EJ series engines. Its really just mix and match till you get a combo that works. Well the issue with that is I don't have a bunch to mix and match with. I am very lucky to have a 03 WRX sitting in my garage that I am currently replacing an engine in at the same time. I can probably manage to use it for some referance.

I know, its been alot of reading, with not alot accomplished. Consider this my thread to gather all the scattered info on this forum and others into a single section.

Any and all imput is appriciated.

If you have done a custom turbo swap, please leave me and everybody else reading this some info about what you chose, how you did it, and why you chose/did it that way.

Thanks a bunch! :smt006

-Kirby

[grayguy]

You are correct about the Wrx intAke not bolting to your heads, it won't work. If you can track down an EJ20k intake that will bolt your 25d heads and have the raised intake arches for the turbo inlet. But, there is also a different throttle body and IAC and fuel system. I'm not sure what all is entailed in getting the 20k Mani to work, I have this exact setup in my garage bolted together, 25d heads tapped for water/oil and a 20k intake bolted on with the 25d throttle body. In theory, it should be possible to get all the stock 25d wiring to work on the 20k Mani, but your probably going to end up modding things like injector plugs and what not to work. Which leads me to my next point.

What point is there to getting a turbo motor in the car and running on your stock 25d ECU? Besides building a
Car in stages and running it non turbo until you have more $$$ I don't see a point. The stock ECU won't be any good to run a turbo. Piggy backs are a waste of time too.

When I built my EJ22T/25D hybrid I used the stock 25d intake/ wiring, and I spent About $1200 on a LINK ECU standalone system and wired it in under the dash. I also had to run new wires for boost control, MAP sensor, and an IAT sensor. It wasn't too hard, far easier than merging 2 stock harnesses (at least for me). When I started my custom swap/build I had about $6k saved for it, and I used all that up pretty quick ($1200 stand alone, 400 wide band O2 / datalogger, $600 clutch setup, $650 head work, $1200 miller MIG setup, $350 eBay exhaust, $400 deatschwerks 810cc Sr20 injectors, and the list just goes on and on...) and basically when it was all said and done, it would have come out about the same power level as a s lightly nodded WRX.

Basically, if I knew then what I knew now, I would have gone straight to a WRX swap. I would have paid my friend at numbchuxconversions.com to do the merge, and I could have dropped the swap in in no time and easily come out way further ahead than I did with the route I went.

PS, don't bother with a 2.0, go EJ255, EJ257 or EJ22t.

[mike-tracy]

EDIT: grayguy posted while I was typing this, so sorry if anything is repeat info.



Hi Kirby, I'm not an expert on what you're talking about by any means, but here's a few comments:

What electrical system will you be using? The WRX/etc ecu won't be able to read the phase I cam and crank sensors. Apparently there's more to it than just swapping the sprockets & sensors, as reddevil had to custom make his to get them to work with newer electronics.

The EJ25D heads on an EJ20 block is less than ideal and will cause detonation (among other things that I can't remember atm) due to the hugely different size bores (99.5mm vs 92mm). The combustion chamber size and shape of the 25D heads contribute to the problem. On an ej22T with the bore of 96.9mm, the problem is lessened especially when most running that combo have the stock retarded 22t ecu. Note this is from info I gleaned from nastisox and the bbs, not my personal experience.

Crossover pipe isn't really an issue, all ej short blocks have the same spacing for the coolant holes on the topside. I personally used the 22t one since the sensors were on the same side as my wiring harness. I cut a very tiny insignificant part off the intake manifold (an ej25d) that was in the way of one of the coolant sensors. Had I used the ej25d pipe, I wouldn't have had to cut anything, but would have needed to extend the coolant temp sensors to fit to the opposite side.

I have an ej20k intake manifold with all the pieces, and out of curiosity I tried to fit its oem turbo inlet (under manifold type) on my ej25d IM. Without significant bending/rerouting of the fuel lines this won't work, and I kind of doubt it will fit at all as the ej20k IM is noticeably taller. Perhaps with a flexible silicone intake it'd work.

SOHC ej22t intake manifold won't fit your dohc heads, but all phase I dohc IM's will.


Selling the EJ20K intake manifold if you're interested.

[grayguy]

Also, with the WRX swap you still have tons of room to grow, because with openecu software you can practically get any setup to work with the stock Wrx ECU. But don't forget, if you make much more than stock Wrx power you need to spend about $3-5k on an 6mt swap to hold the power, which is the reason I've lost all desire to build any Subaru over about 250whp, and no longer have any plans to build another turbo Subaru and am going with stock EG33 H6 power, it's not worth the time/work/investment to me to build a high horse power Subie.

[LGT Kirby]

I really appriciate all the info guys.

Grayguy- In your "ps" you said don't bother with the WRX 2.0. You were referring to the 2.0 with the 2.5 heads. Correct? I didn't realize the bore size was that substantial.

I really don't know how to explain it, but I'm not after huge power. In all honesty, the smart and most efficient thing to do here is to buy a wrecked STi and just have at it. I've seen them go fo $9000 or so, plus or minus depending on the damages. At that point, I would be about 18k into my car. Thats about the price of a low mileage STi as is right now.

Damn my addiction to turbo spools..

[grayguy]

I was saying don't bother with the usdm 2.0 shortblock at all, stock heads or 25d heads. It seems they are getting old/ high enough miles that every time you look at a 2.0 funny it spins a rod bearing or something else goes. My friend has a pile of probably 10+ 2.0s that he's pulled out of 02-03 WRXs in the last year.

[LGT Kirby]

Thats what my WRX is getting done to it. Previous owner spun a bearing, ran it more until the bearing totally went away, and now it has an awesome rod knock.